The present invention relates to measuring human/mechanism interfaces, and more particularly to such measuring systems that relate to the measurement of relatively small one degree of freedom mechanisms, such as switches.
As the market for sales of products becomes more competitive, a manufacturer must distinguish its products from the competition. Thus, a product design may require more than providing the proper function—it may also require providing a certain feel or image for the product. For example, a small mechanism, such as a switch, may need to not only perform its function of adjusting the operation of a product, but also provide a certain feel to the switch operator while being actuated. Such a switch feel may give an impression of quality or distinctiveness to the product, and one may wish to have this particular feel for all of the switches on a given product. Thus, the feel of a switch may be almost as important as the function the switch performs. In order to define and achieve this feel, the human/machine interface for that particular switch must be defined and one must be able to test a switch to determine if it meets the desired definition. Consequently, an accurate and repeatable way to define and measure switches is needed.
Conventionally, measurements for determining characteristics of switches were accomplished by mounting the switches in laboratory type fixtures and connecting them to a switch measurement device. Typically, these measurement devices measured the peak force that was applied during switch actuation and possibly also the range of motion. Mostly, though, the feel of such switches is determined by consensus in panel studies. This conventional approach, however, does not produce a quantitative and repeatable means for completely defining the feel of a switch.
As a result, some of the more advanced systems will employ a laboratory type fixture with a more advanced measurement device that can measure the force applied to the switch as the switch moves through its range of motion. This force/displacement profile (or torque/displacement for a rotary switch), then, provides a more complete definition of the switch properties. And, since the fixtures are tailored to the switch being measured, the accuracy and repeatability can be high.
However, the laboratory type fixtures have drawbacks. This measurement will not take into account the effect of the switch being mounted in the actual product where it will be used—so the affect of the mount on the switch force/displacement characteristics is not taken into account. Thus, the switch, in service, may not have the same feel to an operator as was intended. Moreover, extra time must be taken to disassemble the switch from the product and mount it in the fixture. And, if one wishes to measure the switch after installation on the product at the factory, as a form of quality control, disassembling the switch from the product will defeat this purpose. This is particularly undesirable for measuring switches used in large products, such as vehicles. If one wishes to test switches after installation in a vehicle to make sure they meet their design specifications, then removing the switches for measurement would be very undesirable.
Some have attempted to develop small devices that can be used for such purposes, but they are simple, actuated by hand, and only measure force information, and no position or velocity date, during the switch actuation. But even these simple measurements can regularly have errors as high as thirty percent due to misalignment problems that are common and the non-repeatable nature of human powered actuation. Since, within or on the product, it can be very difficult or impractical to employ a laboratory type fixture that will assure very accurate alignment of the switch relative to the measuring apparatus, the misalignment of these small devices can regularly produce results with significant errors. This makes these small devices unsuitable for meeting the requirements of future products.
Thus, it is desirable to have a small portable switch measurement device that overcomes the drawbacks of prior portable devices, yet provides the complete and accurate results of more advanced laboratory type fixtures and measurement systems.